Photocatalysts employing titanium oxide are widely used by virtue of low price; high chemical stability, high photocatalytic activity, such as organic compound degradability or anti-bacterial property; non-toxicity to the human body; etc.
It has been known that a mixture of titanium oxide with metallic copper or a copper compound, or a product of titanium oxide on which copper or a copper compound has been deposited, serves as an excellent photocatalyst or an excellent anti-viral agent.
For example, Patent Document 1 discloses use of nano particles of a compound MnXy for suppression and/or prevention of infection with viruses. Examples of the nano-particle compound include TiO2, Cu2O, CuO, and combinations thereof.
Regarding the aforementioned combinations of titanium oxide with metallic copper or a copper compound, the crystal structure type of titanium oxide has been studied, and the anti-viral performance of the photocatalysts has been enhanced by use of anatase-type titanium oxide.
For example, Patent Document 2 discloses an anti-bacterial photocatalytic aqueous coating material in which a metal such as copper is deposited on a photocatalyst such as titanium oxide. Patent Document 2 also discloses that titanium oxide preferably has an anatase-type crystal structure.
Patent Document 3 discloses a phage/virus inactivating agent formed of anatase-type titanium oxide containing copper at a CuO/TiO2 (ratio by mass) of 1.0 to 3.5. The invention of Patent Document 3 was accomplished with respect to the finding that copper-containing anatase-type titanium oxide can inactivate phages/viruses.
Regarding the aforementioned combinations of titanium oxide with metallic copper or a copper compound, the valency of the copper compound has been studied, and a monovalent copper compound has used as the copper compound.
Specifically, it has been known that monovalent copper exhibits excellent microorganism- and virus-inactivating performance without use of another component, whereas divalent copper has no microorganism- and virus-inactivating performance. Based on this known fact, a monovalent copper compound is used in the combination of titanium oxide with copper or a copper compound.
For example, Patent Document 4 discloses an anti-viral coating material, characterized by containing a monovalent copper compound as an active ingredient which can inactivate viruses. Patent Document 4 also discloses that the monovalent copper compound inactivates a variety of viruses through contact therewith.
Patent Document 5 discloses a microorganism inactivating agent which contains a monovalent copper compound as an active ingredient for use in inactivation of microorganisms in a short time. Patent Document 5 also discloses another microorganism inactivating agent which contains a monovalent copper compound and a photocatalytic substance. The photocatalytic substance may be a titanium oxide catalyst. Patent Document 5 further discloses that a monovalent copper compound exhibits a remarkably strong microorganism-inactivating effect, as compared with a divalent copper compound.    Patent Document 1: Japanese Kohyo (PCT) Patent Publication No. 2009-526828    Patent Document 2: Japanese Patent Application Laid-Open (kokai) No. 2000-95976    Patent Document 3: Japanese Patent Application Laid-Open (kokai) No. 2006-232729    Patent Document 4: Japanese Patent Application Laid-Open (kokai) No. 2010-168578    Patent Document 5: Japanese Patent Application Laid-Open (kokai) No. 2011-190192